Elastin will be isolated from pleural and parenchymal samples of human lung tissue obtained from subjects of different ages. The elastin preparations will be analyzed for amino acid composition including the cross linking acids desmosine, isodesmosine, merodesmosine, and lysinonorleucine. This study will determine whether lung elastin varies in composition with age as previously reported. Studies of experimental emphysema induced in the hamster by intratracheal injection of elastase will be continued. Protocollagen proline hydroxylase activity will be measured in the lungs after elastase injection to determine whether this enzyme stimulates the synthesis of collagen. Efforts will be directed toward development of a radioimmuno-assay for elastase which has exquisite sensitivity. This may permit cellular localization of the enzymes within the lung following the injection of elastase intratracheally. Examination of the ultrastructure of elastase emphysema is being studied by scanning and transmission electron microscopy. Effort continue for the isolation and characterization of both collagenolygic and elastolytic enzymes from the polymorphonuclear leukocytes and from alveolar macrophages. The metabolism of collagen and elastin is being studied in th lungs of hamsters who were injected with radioactive C14 - Lysine during the first two months of life.